1. Field of the Invention
The invention relates to optical components having waveguide taps. In particular, the invention relates to waveguide taps having a light sensor for monitoring light signals on waveguide.
2. Background of the Invention
A variety of optical components include one or more waveguides where light signals are constrained. These optical components can include one or more tap waveguides. A tap waveguide extracts a portion of the light signal traveling along a primary waveguide. A light sensor is positioned to receive the light signals traveling along the tap waveguide. Because the tap waveguide carries a portion of the light signal traveling along the primary waveguide, the output of the light sensor indicates characteristics of the light signal on the primary waveguide. As a result, the light sensor is monitored to sample the light signals traveling along the primary waveguide.
The tap waveguide typically ends at the edge of an optical component. The light sensor is positioned at the edge of the optical component over the end of the tap waveguide. As a result, the light sensor receives the light signals directly from the tap waveguide. As the complexity of optical circuits formed on optical chips increases, many tap waveguides can not be terminated at an edge of an optical component. As a result, the prior art taps can often not be employed with complex optical circuits. Hence, there is a need for a waveguide tap that is suitable for use with complex optical circuits.
Many tap waveguide arrangements are associated with an undesirably high level of polarization dependent loss. Polarization dependent loss is a result of different polarization modes traveling from the primary waveguide to the light sensor differently. As a result, the relative powers of the polarization modes received by the light sensor is often not representative of the relative powers of the polarization modes in the primary waveguide. Because the distribution of polarity modes received by the light sensor is often not representative, the output of the light sensor can provide poor results when used to monitor an optical component. Accordingly, there is a need for a tap waveguide arrangement where output of the light sensor represents the conditions in the primary waveguide.